Duplex plunger metering pump



March 1967 T. B. MARTIN DUPLEX PLUNGER METERING PUMP Filed Feb. 28, 19662 Sheets-Sheet 1 INVENTOR. M04445 5. Moan/v Filed Feb. 28, 1966 T. B.MARTIN DUPLEX PLUNGER METERING PUMP 2 Sheets-Sheet 2 INVENTOR. 71/0444!5. 114427741 United States Patent 3,310,000 DUPLEX PLUNGER METERING PUMPThomas B. Martin, Micro-Pump C0rp., R0. Box 392, Danville, Calif. 94526Filed Febi 28, 1966, Ser. No. 530,703 Claims. (Cl. 103171) Thisinvention relates to a new and improved duplex plunger metering pump andis a continuation-in-part of co-pending application-s 350,306 filed Mar.9, 196-4, and 350,503 filed Mar. 9, 1964, now Patents Nos. 3,238,878 and3,238,883, respectively.

More particularly the present invention comprises a high pressuremetering pump having a number of advantages over conventional pumps ofthis general type.

One of the principal advantages .of the construction hereinafterdescribed in detail is the fact that the drive shaft is hermeticallysealed from and magnetically coupled to a rotating driving means such asan electric motor. This arrangement does not require a rotary shaft sealand consequently the likelihood of leaking, wear or sticking is reducedand the imposition of undue loads on the driving motor and generation ofdestructive amounts of frictional heat are likewise eliminated. Thedrive for the pump is two concentric magnets, one driven by a motor andthe other mounted on the pump shaft. Although the gap between themagnets is small, nevertheless, it is suflicient so that a partition maybe interposed between the two magnets to serve as a seal and thuseliminate the conventional rotary pump seal interposed between the pumphousing and the shaft which extends exteriorly of the pump housing andwhich frequently is the cause of leakage and other undesirable features.1

A further feature of the construction is the fact that the sealed pumpassembly may be removed intact from the motor and replaced with anotherpump of the same or different design without interference with thedriving motor. Conversely, the motor may be replaced withoutinterference with the pump and its associated piping.

A still further advantage of the present invention is the fact that thepump is self-priming against a high discharge pressure.

A still further feature of the invention is the fact that the pump canhandle liquids with entrained gases at high discharge pressure, therebydiffering from conventional pumps of this class.

Still another feature of the invention is that, with proper choice ofresistant materials, the pump can handle liquids which are ordinarilycorrosive to pumps of this class.

A still further advantage of the invention is the fact that it has apowerful suction and can be used in vacuum pump applications.

A still further advantage of the invention is the low cost ofconstruction of the pump, its simplicity of construction and the easewith which it may be maintained and repaired. Particularly, the pump maybe examined and parts replaced without disconnecting the pump casingfrom piping to which the input and discharge ports are connected.

Still another advantage of the invention is freedom from excessive wearof the moving parts by reason of the construction of the pump ashereinafter set forth.

Other objects of the present invention will become apparent upon readingthe following specification and referring to the accompanying drawingsin which similar characters of reference represent corresponding partsin each of the several views.

In the drawings:

FIG. 1 is a longitudinal vertical sectional view through the pump.

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FIGS. 2 and 3 are, respectively, transverse sectional views takensubstantially along the lines 22 and 33 of FIG. 1.

FIG. 4 is a fragmentary sectional view taken substantially along theline 44 of FIG. 1.

FIG. 5 is a view similar to FIG. 3 of a modified construction.

The pump which is the subject of this invention has a body or casing 11formed with an inlet port 12 and discharge port 13 threaded as indicatedat reference numerals 14 and 16, respectively, for attachment to inletand discharge pipes (not shown). Extending longitudinally centrally ofcasing 11 is a bore 17 for rotary drive shaft 18. The means wherebyshaft 18 is rotated is hereinafter described in detail. At the forwardend of Casing 11 is a crankcase chamber 19 which opens into the forwardend of the pump and is closed off by a front cover 21 with a gasket 22interposed between the cover and the front end of the casing. Extendinglaterally in diametrically opposed directions from crankcase 19 arecylinder bores 23 which are closed off by cylinder heads 24L and 24Rheld in place by screws 26. The outer end of shaft 18 is provided withan eccentric 27 which is received in slider 28 formed of an antifrictionmaterial such as a composition of Teflon, glass fiber and molybdenumdisulphide, or equivalent material. Slider 28 has curved opposedcircular arcuate edges 29 and, displaced therefrom, flat side edges 31.Slider 28 is re ceived in the rearward recessed face 32 of crosshead 33which reciprocates laterally in crankcase 19 as eccentric 27 revolves.Crosshead 33 is formed with a transverse bore 34 to receive plunger 36which is held therein by set screw 37. Accordingly, plunger 36 isprovided with a substantially transverse reciprocating motion. To avoidimperfections in alignment, provision is made for a slight rocking ofplunger 36 by means hereinafter described.

Mounted in each lateral bore 23 is cylinder 41 having a central bore toreceive plunger 36 with an exceedingly close fit. The inner end ofcylinder 41 has an outside diameter less than the inside diameter ofbore 23 and the cylinder is further formed with radial passageways 42providing communication between crankcase 19 and bore 23 to the centralbore 43 of cylinder 41. The passages a 42 comprise in effect ports forthe chamber 43 of cylinder 41. The outer end of cylinder 41 has anenlarged head 44 which seals against an O-ring 46 recessed in body 11and the outer end of cylinder 41 is formed with a conical surface 47which seats against the inner end of hole 48 in head 24L or 24 R. Byreason of the conical surface 47 engaging the hole 48, the cylinder 41may rock slightly, this movement being necessary to prevent binding ofplunger 36 in bore 43 of cylinder 41 as a result of imperfections inalignment.

In the modification best shown in FIG. 3, hole 48 is provided with aresilient ball 49 biased by means of spring 50 in the bottom of hole 48against the open end of hole 43 of cylinder 41.

The flow of fluid through the pump is accomplished as follows:

Fluid enters intake port 12 through threaded opening 14 and is deliveredinto crankcase 19 by means of duct 51 in body 11. From crankcase 19 thefluid flows through the opening between bore 23 and cylinder 41 andthrough ports 42 into the bore 43. As plunger 36 moves to the left asshown in FIG. 3, the port 42 on the left-hand side is closed and thefluid entrained in the bore 43 is compressed. When the pressureovercomes the force of spring 50, the ball 49 is lifted from its seat atthe opening of hole 43 and the fluid flows into hole 48 and thencethrough a notch 52 into the oval-shaped cavity 53 in the inner face ofhead 24L. Seal 54 assumes the oval shape 3 of the cavity 53 and sealsagainst the end of body 11, all as best shown in FIG. 4.

Referring now to FIG. 2, fluid from cavity 53 on the left sideco'mmuicates by angularly disposed drill hole 561., 56R to the cavity 53on the right-hand side and thence by duct 55 (see FIG. 1) to dischargeport 13 and thence through threaded connection 16 to the discharge pipe(not shown). On the reverse stroke of plunger 36, as soon as thepressure in bore 43 drops below the force of spring the ball 49 seatsand closes ofl? cylinder bore 43. Thereafter, an additional quantity offluid is drawn into bore 43 through port 42 in anticipation of the nextleftward movement of plunger 36. Meanwhile, the rightward movement ofplunger 36 forces fluid from the right cylinder bore 43 into chamber 53and thence through duct 55 into the discharge port 13.

Rotation of shaft 18 may be accomplished in various ways. A preferredmeans is similar to that shown in copending application Ser. No.350,306. An annular ceramic magnet 71, preferably having two north polesand two south poles, is mounted on the exterior end of shaft 18.Surrounding the exterior of magnet 71 is a nonmagnetic, cup-likepartition 73, preferably a poor conductor of electricity. Austeniticstainless steel is satisfactory in most applications, although aconductive material such as brass may be used when speed is notexcessive. Thus, shaft 18 and magnet 71 are sealed by means of partition73 without the use of rotary seals common in other rotary pumps and thedisadvantages of rotary seals are eliminated. The fluid being pumped maybe circulated throughout partition 73 and around magnet 71. For suchpurpose, a hole 78 may be formed communicating from inlet port 12 andthe cavity 79 in which magnet 71 rotates and a return passage 81 may beformed surrounding shaft 18 and communicating with crankcase 19.

Magnet 71 as well as drive magnet 82 is a barium carbonate materialhaving incorporated therein a considerable mass of magnetic materialsuch as iron oxide. Such magnets are produced, among others, byStackpole Carbon Company under the trademark Cera Magnet. It is acharacteristic of such magnets that a plurality of poles may besubstantially permanently magnetically induced therein. The magnets haveextreme resistance to demagnetization and high electrical resistivity.Eddy current losses are negligible. The number of poles per magnet issubject to wide variation, but in the form herein illustrated, there arepreferably two north and two south poles in each of the magnets. Themagnets are concentric about the axis of rotation of shaft 18.

The driving motor 83, especially in small sizes, may be a shaded poleinduction motor having the axis of shaft 84 in line with the axis ofpump shaft 18. Hub 86 is fixed to shaft 84 by any means and is staked tobell-shaped hub 88 which fits around the outer periphery of magnet 82.An adaptor housing 91 is secured to the outer end of motor 83 by bolts90. Adaptor 91 may be of a die cast material and dilferent shapes ofadaptors may be provided to be substituted with different shapes andsizes of standard motors, thus making the pump interchangeable for suchmotors. The outer flange 92 of adaptor 91 is connected to annular plate93 by bolts 94, O-ring 96 sealing the inner end of cup 73 to body 11 andbeing held in tight engagement by means of ring 93. A spacer ring 97centers the motor sub-assembly relative to the pump sub-assembly. Byremoving bolts 94 the motor and pump may be interchanged withoutdisplacing the other member. Adaptor 91 may be provided in differentshapes to make the pump interchangeable for various styles of motors.

As further simplification of the inspection and maintenance of the pump,the plate 21 and the cylinder heads 24L and 24R may be individuallyremoved and the interior parts of the pump inspected and replacedwithout disconnecting the piping from fittings 14 and 16.

In FIG. 5, a modification is. shown which is particularly suitable forhigh pressure gas or suction installations. Because many of the partsare similar, the same reference numerals are employed as in thepreceding modification. Ball 49 is, however, replaced in thismodification. In lieu thereof, there is substituted a cupshape member101 faced with a resilient disc 102 which seals against the outer end ofcylinder 41. Spring 50 biases cup 101 and facing 102 against thecylinder. In pumps of this type the minimization of the space betweenthe end of the plunger 36 and the check ball 49 is desirable and suchresult is achieved in the modification of FIG. 3. In FIG. 5, however,the space is all but entirely eliminated in that the stroke of plunger36 may actually engage face 102 and lift the cup 101 against the forceof spring 50. Accordingly, an extremely small clearance volume isachieved and gas bubbles between the plunger and the discharge checkvalve are more efiectively ejected.

In both of the modifications heretofore described, the pump isself-priming even against a very high discharge pressure in thedischarge pipe. Liquids having entrained gasses can be handled becauseof the minimization of space for air or gas bubbles in the cylinder atthe end of the discharge stroke of the pump.

Although the foregoing invention has been described in some detail, byway of illustration .and example for purposes of clarity andunderstanding, it is understood that certain changes and modificationsmay be practiced within the spirit of the invention and scope of theappended claims.

What is claimed is:

1. A duplex metering pump comprising a casing formed at one end with apump crankcase, a shaft, means for rotating said shaft in said casing, aplunger having pistons at opposite ends reciprocable in said crankcase,said plunger being a unitary member, means for transmitting rotarymotion of said shaft into reciprocating motion of said plunger, a pairof ported cylinders mounted at opposite sides of said crankcase, eachsaid cylinder receiving one said piston mounted at opposite sides ofsaid crankcase and extending diametrically oppositely transverse to saidshaft, cylinder heads on said casing, each forming a discharge chamberadjacent the outer end of said cylinder, check means in each saiddischarge chamber, resilient means biasing said check means to close offthe outer end of said cylinder, means forming an inlet port into saidcasing, said casing formed to transmit fluid from said inlet port to theport of each said cylinder, said plunger arranged so that alternatelyeach said piston on its discharge stroke first closes the port in itscylinder and then expels fluid in said cylinder past said check meansagainst the force of said resilient means into said discharge chamberand then on its suction stroke releases said check means to closedposition and draws fluid from said crankcase into said cylinder andmeans forming a discharge port to receive the discharge from each saiddischarge chamber, said pistons on each discharge stroke coming intoclose proximity with said check means, communication from each saidcylinder to its corresponding discharge port being direct with saidcheck means immediately beyond said cylinder, whereby the space betweensaid piston at the end of its discharge stroke and said check means issubstantially nil.

2. A pump according to claim 1, in which said check means comprises aball.

3. A pump according to claim 2, in which said ball is resilient.

4. A pump according to claim 1, in which said check means comprises aflat-surfaced member engaging the outer end of said cylinder, saidpiston on its discharge stroke extending into close proximity to saidflat-surfaced member.

5. A pump according to claim 1, which further comprises a first magneton said shaft, a second magnet in proximity to said first magnet, meansfor rotating said second magnet to turn said first magnet andreciprocate said plunger, said first magnet being annular, said secondmagnet annular and surrounding said first magnet, and a non-magneticseal sealed to said casing and interposed between said magnets.

References Cited by the Examiner UNITED STATES PATENTS 1,535,643 4/1925Astrom 103l66.5 2,068,392 1/1937 Acker 103171 2,420,850 5/1947 Yuza103153 6 2/1959 Kifler et a1. 103171 2/1961 Berner 103103 9/1961 Swensonet al 10387 3/1965 Bennett et a1 103228 FOREIGN PATENTS 12/ 1955 France.

4/ 1963 France.

10 DONLEY J. STOCKING, Primary Examiner.

HENRY F. RADUAZO, Examiner.

1. A DUPLEX METERING PUMP COMPRISING A CASING FORMED AT ONE END WITH APUMP CRANKCASE, A SHAFT, MEANS FOR ROTATING SAID SHAFT IN SAID CASING, APLUNGER HAVING PISTONS AT OPPOSITE ENDS RECIPROCABLE IN SAID CRANKCASE,SAID PLUNGER BEING A UNITARY MEMBER, MEANS FOR TRANSMITTING ROTARYMOTION OF SAID SHAFT INTO RECIPROCATING MOTION OF SAID PLUNGER, A PAIROF PORTED CYLINDERS MOUNTED AT OPPOSITE SIDES OF SAID CRANKCASE, EACHSAID CYLINDER RECEIVING ONE SAID PISTON MOUNTED AT OPPOSITE SIDES OFSAID CRANKCASE AND EXTENDING DIAMETRICALLY OPPOSITELY TRANSVERSE TO SAIDSHAFT, CYLINDER HEADS ON SAID CASING, EACH FORMING A DISCHARGE CHAMBERADJACENT THE OUTER END OF SAID CYLINDER, CHECK MEANS IN EACH SAIDDISCHARGE CHAMBER, RESILIENT MEANS BIASING SAID CHECK MEANS TO CLOSE OFFTHE OUTER END OF SAID CYLINDER, MEANS FORMING AN INLET PORT INTO SAIDCASING, SAID CASING FORMED TO TRANSMIT FLUID FROM SAID INLET PORT TO THEPORT OF EACH SAID CYLINDER, SAID PLUNGER ARRANGED SO THAT ALTERNATELYEACH SAID PISTON ON ITS DISCHARGE STROKE FIRST CLOSES THE PORT IN ITSCYLINDER AND THEN EXPELS FLUID IN SAID CYLINDER PAST SAID CHECK MEANSAGAINST THE FORCE OF SAID RESILIENT MEANS INTO SAID DISCHARGE CHAMBERAND THEN ON ITS SUCTION STROKE RELEASES SAID CHECK MEANS TO CLOSEDPOSITION AND DRAWS FLUID FROM SAID CRANK-